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Replace 5kwGenny with high output alternator
Posted: February 23rd, 2025, 7:07 pm
by GFB
Hello!
Looking for input. Couple of years ago I set up solar on my boat, works like a charm. I can last on the the hook up to 5 days without worrying about charging.
My Kholer generator has broken down, and am thinking of ripping it out of the boat.
I would replace it with a high output alternator on 1 of my engines. I am using the Integral epower alternator as an example.
Running the 1 engine for appox 1 hour at min 1800rpm would generate 8-9kw (according to their literature).
Why would I not just get rid of the Genny, take it out of the boat and rely on 1 engine to run for 1 hour per week to recharge my batteries (LIFPO batteries).
Genny is currently broken, going to take 2k$ to fix.
I could sell it for half that, fund the alternator for nothing - or at least close to it.
BTW: Some facts
Don't use AC unless on shorepower. Ever.
Rarely use hot water on the hook, swim to bathe. Bio deg soap.
Wash dishes in cold water. Why not.
So... what use is the Genny?
All opinions and thoughts appreciated before I go ahead this spring.
Thanks for helping ahead...
Re: Replace 5kwGenny with high output alternator
Posted: February 23rd, 2025, 8:00 pm
by bud37
On the face of it, for your use it would be fine considering on how you plan to operate your boat. I do like the idea of getting away from those high rpm generators.
So here goes.... the but for me would be on the sale of the boat when comes time.....other folk may want air and hot water etc. I remember considering one boat on GBay, we really liked the boat but it had no air or generator....we could not get past that and moved on , fyi... that boat sat for a very long time for sale. Just something to consider.
Re: Replace 5kwGenny with high output alternator
Posted: February 23rd, 2025, 8:05 pm
by GFB
hmmm. Correct, I have heard that before. I've noticed though that the mfg's are doing away with Genny's due to these consideratios.
Honestly tied up in knots (Pun) over that particular point.

Re: Replace 5kwGenny with high output alternator
Posted: February 23rd, 2025, 8:59 pm
by Carverlvr2
Not sure there is a trend away from gennys. I just finished a long search for our “next boat” (there’s always a Next One) and noticed many manufactures of mid size (more than just a day cruiser or single overnighter) switching to diesel, low rpm gennys for lower noise/emissions and longer life. For most of us where AC and hot water are more than just niceties, Lipo and inverters just aren’t quite there yet. Much better chance the next buyer will want those features and a genny to power them. Just my thoughts.
Re: Replace 5kwGenny with high output alternator
Posted: February 24th, 2025, 10:52 am
by paulr
When up for resale take $20,000 off the price.
Re: Replace 5kwGenny with high output alternator
Posted: February 24th, 2025, 11:36 am
by Viper
Ya I agree. You should see the small boats they're squeezing generators into these days. Let's face it, we're a lot more power hungry than we were a few years ago and that's not going to change, if anything we'll want more power with all the conveniences we're used to having on land and can't seem to do without on the water.
Re: Replace 5kwGenny with high output alternator
Posted: February 28th, 2025, 5:51 pm
by Alanna Mo Cree
What is being proposed is essentially how we will produce power in my electrical upgrade:
viewtopic.php?f=13&t=8481Resale is definitely a consideration, and I would not be planning to remove the generator except that
1. We are replacing it with a system that will still allow full AC and A/C at anchor for at least a day (depending on the math maybe as much as 3 days, but I'll believe it when I see it).
2. We are planning to keep the boat at least another ten years. This timeframe is important because that will be about the time that the batteries are ready to be changed, and I anticipate that the technology will be at a point that the next set of electrical storage will be able to fully replace a generator. The technology is very close, but I'm still a little skeptical.
3. A generator replacement would be over half as much as the cost of the electrical upgrade.
We are going with two high output alternators not because we need 18KW of electrical generation, but because of redundancy and load balancing. I can run the entire boat and charge batteries on only one engine, and can also alternate which engine so I'm not always running the same one for generator duty.
I could be completely wrong in my plans and will probably know in about a month or so when the project is completed.
Re: Replace 5kwGenny with high output alternator
Posted: March 1st, 2025, 2:25 pm
by bud37
I wonder if replacing the old genny with a low rpm diesel genny could work....really wouldn't need much a fuel tank....much cleaner exhaust as far as Carbon Monoxide is concerned etc. and easy power for a/c when ever and for how long as ya need.
Ah, just a thought. Perhaps the pricing would change that idea perhaps, but I really don't know at this point. Sometimes convenience is worth a lot, IMO.
Re: Replace 5kwGenny with high output alternator
Posted: March 1st, 2025, 6:24 pm
by Carverlvr2
Bud, I agree. Low rpm diesel seems to be the new go to option. Very hard to even find gas marine generators for replacement. Diesel is just safer all around. If/when my Kohler gas 7.3e fails o the point of replacement vs repair, I’ll look closely at diesel replacement or hopefully something like solid state batteries or hydrogen cells are more mainstream.